224 



is situated immediately on Ihe proximal side of tlie latter, the one corresponding 

 to the large avicularium is placed basally to its proximal part (fig. J h), and a 

 similar tiiougli not always as obvious a displacement ol' liiis lateral chamber may 

 also be seen in a greater or smaller number of the single zooecia, which may 

 follow the daughter-zocvcium of the bizoa'cial segment. With exception of the 

 above mentioned case the scapular clramber of the other zoa-cia is generally 

 more or less incompletely calcified, and the calcareous walls, separating the com- 

 l)lete avicularium from the supra-scapular and tlie infra-scapular chambers, are 

 either altogether wanting or but incompletely developed. This cliamber is gener- 

 ally least developed on the inner side of the zoa'cium (fig. 1 g) immediately suc- 

 ceeding the often mentioned daughter-zowcium. It is here mostly membranous 

 and ditfers from the pedal chamber in one thing only, viz. that the surrounding 

 marginal ridge in its frontal part terminates generally in a more or less devel- 

 oped spear-shaped process. In all the otlier cases (figs. 1 f, 1 e, 1 i), where this 

 lateral chamber is not developed as an avicularium, its distal and frontal walls 

 are membranous and only the lateral walls are calcified to a greater or lesser 

 extent in dilTerent zoa^cia, forming thus two, as a rule triangular calcareous la- 

 minae connected with each other under an outwardly directed angle. 



While, in this species, it is not difficult to decide the position of the various 

 lateral chambers in the solitary zocrcia, the case is a little more complicated with 

 respect to the bizooecial segment, as the daughter-zoa-cium, which has lateral 

 cliambers of its own, must according to its position be regarded as the adzooecial, 

 scapular chamber of the mother-zoa^cium. As regards the two abzoa-cial lateral 

 walls, of which one belongs to the mother-zocrcium the other to the daughter- 

 zocccium, there can be no doubt, that the distal cavity corresponds to the three 

 first, here unseparated lateral chambers, while the proximal one is the pedal. 

 There then remain two lateral chambers, which are at the same time bounded 

 by the mother- and the daughter-zocccium (fig. 1 b), a distal one, mostly bounded 

 by the distal part of the adzo(Ccial lateral wall of the daughler-zotrcium, which 

 has about 8 rosette-plates, and a proximal one, mostly bounded by the proximal 

 part of the adzocecial lateral wall of the mother-zocecium, which is provided 

 with G— 7 rosette-plates, and only to some extent by the proximal, truncated end 

 of the daughter-zoa^cium. The distal chamber, the frontal wall of which is parti- 

 ally calcified and thus forms a triangular or rounded triangular calcareous lamina 

 beside the aperture of the daughter-zoa>cium, is in exactly the same relation to 

 the daughter-zocccium as the supra-scapular chamber is to the avicularium and 

 must accordingly be regarded as the supra-scapular chamber of the mother-zoa'- 

 cium. The jiroximal of the two cavities may with as much certainty be con- 



